IPhone 5 very poor battery life?

Hi
My parents bought me an iPhone 5 for Christmas and I have found that the battery life on it is very poor. I have had no phone since October after I dropped my BlackBerry in the bath so I was looking forward to this iPhone (I knew I was getting it)
It is losing up to 20% of power in as little as 25 minutes. Although I do text and play music a lot, I don't think it should be losing this much power in such a short amount of time.

I also have an iPod Touch 4th Gen, iPad 1 and iPad 4 and I play a lot of music, use lots of apps and internet on there too (especially iPod) but they don't lose this much power.

When I turned the phone on yesterday, a software update was immediately available, to fix a bug impacting Wi-Fi. So I installed the update and then started to use the phone.

Does anybody else have any problems with the iPhone 5 battery life or is it just me?

The phone is on a pay monthly contract with O2 if this is relevant.
What should I do?

Thanks
Rileigh x

Added (1). The current iOS is iOS 6.0.2

Added (2). Josh - My mum has had the phone since early November but never turned it on. The first time the phone had ever been switched on was yesterday morning. How can I need a new battery so quickly?

Added (3). I just found this article! Http://www.gmanetwork.com/news/story/287779/scitech/technology/iphone-5-battery-issues-reported-with-ios-6-0-2-update

The iphone does have a decent battery. But smetime batteries can drain over the years. Most mobiles are made in china, so the parts are built anything upto 2 yrs before the phone is actually mad, so sometimes these parts malfunction. And batteries can occaisionally paly up. My advice-get a new battery

My iPhone is dead by the time I get on my lunch break, so it's not only you. My iPad 3 is great and by 10pm it's about 20%. I think it's just the way it is.

Usually the battery drains because of apps constantly running in the background, some of them switch off but others can't. Also, because it has the latest software it needs more battery to run the software, my iPod battery life started running out quicker when i updated it, unfortunately you can't change that. But you can do things like putting the brightness lower and not charging it a lot. I know that sounds weird but if you constantly have it on charge that affects the battery as well, try to charge it as few times possible, like when it gets to 10% and don't leave it on charge all night a lot either, that will mess it up as well.
Oh and you mentioned that it's on contract, if it's 3G that will have an affect as well because it takes quite a bit of battery trying to provide internet wherever you are, the same thing happens to blackberry's as well. If you really really need to save battery switching to 2G would be better but that would be slower.
However, if your iPhone goes from 100% to 20% within minutes then i would suggest taking it back to the shop because it could be a faulty battery

Hope that was helpful. X